Respiration-related afferents to parabrachial pontine regions.

The dorsolateral pons around the parabrachial nucleus is an important participant in respiratory control. This area involves various respiration-related neurons, and their respiratory modulation is thought to arise from afferents from medullary respiratory neurons. Today, however, only a limited number of afferent sources have been identified. First, relatively well-characterized afferents to the pons are those originating from two types of the lung stretch receptors, slowly adapting and rapidly adapting receptors. That is, the majority of the second-order relay neurons of these receptors in the nucleus tractus solitarii project to the pons. Second, certain types of respiratory neurons of the medullary respiratory groups are either known to or presumed to project to the pons. For instance, major inhibitory neurons of the Botzinger complex, augmenting and decrementing expiratory neurons, send afferents to the pons. This article overviews such afferents and discusses their connectivity with pontine neurons.